Automotive hybrid voltage regulator design with adaptive LDO dropout using load-sense technique

A switching converter (DC-DC) cascaded with a low dropout regulator (LDO) gives the best trade off in terms of high system efficiency and low output ripple for automotive power management applications. The dropout voltage of the LDO is fixed based on its peak load. An adaptive LDO dropout technique, based on LDO load-current sensing, has been proposed to improve the moderate and light load system efficiency of the cascaded DC-DC and LDO combination. The feedback from LDO output to DC-DC output is stable and has minimal overhead (< 2%) in terms of area and current consumption. The 1V LDO with adaptive dropout gives an efficiency improvement of 74% for 1A load to 81.6% for 100uA load across input voltage range of 6V to 18V. The overall hybrid regulator efficiency improvement upto 5% is achieved in simulations using 0.35μm AMS H35 process.